There’s more to building your dream house than just laying bricks. Before you even pour the slab, you’ll need to make sure the lot is ready to be built on, and that means site works. But what exactly are site works, and how necessary are they?
Site works is everything done to prepare a lot for building on, including site classification, foundation design and earthworks. The scope of site works will depend on the features and terrain of the block, meaning that costs will vary according to the works needed.
It’s a common myth that site works are a ‘rip-off’ or aren’t really necessary. As experienced home builders will tell you, high-quality site works are one of the most critical parts of the construction process.
You can’t build a stable and long-lasting property without preparing the land thoroughly. There’s no way around it – anyone planning on a new home build in Perth needs to carry out site works on their block before the first brick can be laid.
Keen to understand what site works are and why they’re so important? We’ve gone to the trouble of putting together this article to tell you everything you need to know.
Read on to learn all about site works in construction.
Table of Contents
What Are Site Works?
Site works are everything needed to get your plot of land ready to build on, and includes land clearing, levelling and installing drainage. Building a house is more than just the walls and doors. You need to ensure the land itself is ready and able to support your home.
When building a new home, site works are often done during the pre-construction stage, right after the council and other legislative bodies approve the construction permits. Site works can also be needed during the subdivision process, even if you’re not planning to build yet.
While some site works can be time-consuming, it’s all for the important goal of getting your piece of land ready for a home. Top-quality site work is important since your house’s safety, stability, durability, and efficiency depends on how your lot is prepared to handle the weight and stresses of the structure being built on it.
In most situations, your general contractor oversees the entire site work phase. However, your contractor may subcontract other service providers depending on what your site works call for.For example, it’s pretty common for a general contractor to hire plumbers and pipe layers to work on your site.
When building on a difficult block, including those with unstable ground conditions, site works are more important than ever.
You’ll also find the most extensive site works performed on lots with a steep slope. The extent of site works will depend on what kind of sloping block home design is used.
What Does Site Works Include?
Site work includes all kinds of property works that are not part of your house’s physical structure. Aspects of site works include:
- Site classification by an engineer (eg. soil type, wind loading)
- Site clearing (eg. weed overburden)
- Detailed foundation design created by an engineer
- Earthworks including testing, preparation & compaction of foundation pad
- Preliminary drainage, sewer, and septic work
- Bushfire attack level (BAL) assessment (where applicable)
The type of site works required will depend on the lot itself, as well as the style of home you choose. Double-storey homes will require stronger foundations, for instance, and more extensive earthworks are required to stabilise sloping blocks.
How Much Do Site Works Cost in Australia?
Site costs depend on a multiple of factors unique to the block, so there is no such thing as ‘average’ costs.
On flat lots without any complex requirements, prices for site works start at a minimum of around $12,000 to $13,000. Complexities like effluent treatment systems or clay soil can require site costs of $50,000 to $60,000 or more to resolve. For that reason, getting a site-specific inspection and quote is the best indication of how much site works will cost.
A lot of specific factors are involved in building a house, such as the terrain, soil type, angle, and size of your parcel and structure. These are unique to your site. As such, site work can vary tremendously.
On the other hand, if the site work involves building on a slope, you could find yourself spending significantly more for site works, especially if your site is steep or requires an extensive retaining wall.
Lower site works costs will not include specialised work such as boulder removal, old-structure demolition, filling up old bodies of water, and more.
Site work quotes may evolve too, which is why it’s important to have the site inspected at the very beginning. Your contractor might have unearthed an unforeseen problem or land feature that needs to be addressed. If this happens, your contractor will explain to you what additional site work needs to be done and quote you based on similar projects.
What Affects The Cost For Site Works?
There are a lot of factors that can affect the cost of site works, including:
Site Requirements – Site works aren’t just about getting the land flat for building on, it’s about everything that will make the property livable. Site-specific requirements will affect your total site works cost, including things like:
- Retaining walls needing to be constructed
- The driveway has an incline or decline to the garage
- Upon soil testing, the soil is found to contain rock, limestone, or peat
- Lots of bushes, trees, and vegetation need to be cleared
- Building a more energy-efficient or solar passive home
Site Location – When you are building a home, you spend a long time deciding what neighbourhood you want to live in, and what amenities you want to be near. But the location of your site can affect site works depending on:
- There are easements around your property
- The site is buffeted by high, strong winds
- The site is within a kilometre of breaking surf
- The site rests on a high water table
- The site is subject to noise attenuation requirements
- The site is in an area susceptible to bushfires
- The site is located in a semi-rural area
- The lot is in a Brownfield or established area
Home Specifics – Every home has different specifics. It’s not just about making a home your own, the specific factors of your home’s construction and what type of home it is will all affect your site works costs, including:
- The house is on a battleaxe block or rear lot
- The house being built is tall enough to require scaffolding
- An existing home needs to be demolished
- There are challenges in accessing the site
- The house being built is on top of an underground sewer
- The builder needs to batter the lot to keep the house pad level
If you’re building on a more difficult block, it’s worth working with an experienced custom home builder. A custom builder is more experienced in site responsive design, and can organise the necessary site assessments at the very beginning.
Do Site Works Cost More For A Sloping Block?
Building on a slope requires more specialised equipment and site preparation which means an increase in price to prepare it for construction. The bigger or steeper the slope, the greater the cost.
Although they can be very visually rewarding, building on a sloped block introduces a range of challenges. Without an even, flat surface to work on, specialised tools, machinery and earthworks techniques are required to create an area that is safe to work and build on. While it’s certainly possible to build on a sloped block, it will need land levelling to build a standard home design.
However, some methods of building on a slope are more cost-effective than others. Options such as building on stilts can reduce site costs compared to extensive cut-and-fill work.
You’ll also need to consider whether outdoor areas need earthworks to be liveable spaces. If you have a sloping backyard or front yard this area may need to be levelled or have retaining walls installed.
Ask your building contractor regarding the cost of site works if your property is on a slope. An experienced home builder can let you know which sloping block solutions are best for your lot.
Can The Site Works Cost Change After I Have Signed The Building Contract?
If you work with experienced builders, you won’t find the site works cost changing much at all. Site works costs are estimates made by the builder anticipating what may come up during the preparation of your site. A seasoned builder’s industry knowledge will help avoid surprises.
The reason some site works costs may change is that an issue has come up that the builder didn’t anticipate. This is more common with inexperienced builders who fail to perform proper site assessments at the outset.
When you work with a professional builder, you’ll find that the site works costs rarely increase as time goes on, because they have the experience to identify what may come up during the process of preparing your land.
What Is Site Cost Allowance?
A site cost allowance is a rough estimate for the cost of site works on your land that a contractor provides you at the start of the site works process. If there are any uncertainties about the block, it may be difficult to give a fixed upfront cost, so an allowance is made in the build’s costing to cover it.
The final cost will then be determined after a comprehensive assessment of your property. This may include excavation, soil testing, and engineering services if a block is unstable. Site cost allowances may cover part of or the entirety of site works cost, depending on the amount of work that needs to be done on the plot of land.
To understand the role site cost allowance plays in your building estimate or contract, speak with your builder.
How Long Do Site Works Take?
Normally site works take between two to four weeks to complete. After this, the site will be ready for the concrete slabs to be poured or the foundations erected. However, the duration of site works depends on various factors affecting the site.
Of course, challenges such as slopes, high water tables, high concentration of lime, the need retaining walls, and more can lengthen the duration of the site works. Also, if your site is in a rural area, site works may take longer based on access and availability of services.
It’s also important to note that as the construction of your home progresses, your contractor may need to carry out further site works for complete installation of services and utilities.
Are There Hidden Costs Behind Site Works?
There aren’t hidden costs behind site works, but there are times when site works will be more than a builder anticipated. If there are hidden issues under the surface of your block, such as rock or clay, the scope of siteworks may change during the process itself.
However, working with a skilled and knowledgeable builder will keep surprises to a minimum. This is because more experienced home builders carry out more thorough site inspection and evaluation upfront. You’ll find that cost estimates for the building process are more accurate based on your builder’s industry experience.
Site works are often touted as big ‘hidden costs’ as most homeowners don’t really “see” these works. However, they’re actually critical to the long-term safety and stability of your new property. They are needed so that your house can be built safely on the lot, and it’s impossible to skip them.
It is possible for site works costs to change, but this isn’t a ‘rip off’ – when delving into the soil deep below your block, it’s possible to discover hidden problems that couldn’t have been detected upfront. However, a reliable builder will provide a suitable site allowance in the overall estimate and communicate with you throughout the process if there are any developments.
When planning a new home build, ask your prospective builder upfront how they handle site costs and site allowances. Your builder should be able to set your mind at ease about their thorough site inspection processes.
If you’re not confident your builder is giving you all the facts, consider reaching out to one of Perth’s most experienced custom builders: Central Avenue Homes.
What Are P Class Slabs?
A Class P slab or site means it is a problem site that suffers from significant ground movement because of rapid moisture changes. As such, a class P site is unable to bear the structural load evenly.
Examples of Class P sites include:
- Soft soils such as loose sand, silt, or soft clay
- Cut or filled sites
- Sites that are saturated with moisture
- The soil on the site has suffered erosion
If you need to build your property on a Class P site or slab, it is necessary to consult with a professional structural engineer.
Building a New Home in Perth?
Site works may seem like an unnecessary cost, but it’s vital for the safety and stability of your new home. Trying to cut costs on site works can cause drastic problems with your property in just a few years’ time.
Your building contractor will be able to tell you how they handle site works and site costs through the contract process. A reliable builder should be able to give you confidence in how this part of the build is handled.
At Central Avenue Homes, we have long standing relationships with our trusted site works contractors. We always carry out extensive site inspection before starting the home build process. With decades of experience working on Perth home builds, our expertise keeps site costs as predictable as possible.
If you’re building a new home, you’ll get unbeatable results working with one of WA’s most experienced custom builders. To find out more, contact Central Avenue Homes today!
Greg has over 40 years of experience in the WA building industry starting as a carpenter joiner.
He is entrenched in the local industry and has served on the board for MBAWA (Master Builders Australia WA) for over 10 years and was a founding director of Wesbuilders Cooperative for over 11 years.
With this experience he is able to quote accurately on new projects without the huge increase to provisional sum allowances.